This invention relates to systems for connecting struts and nodes in a three-dimensional structural framework.
Certain three-dimensional structural frameworks employ a plurality of rods or struts arrayed in a particular geometric pattern with their ends connected together at joints or nodes.
A variety of methods for connecting the struts to the joints are known. One method is commonly known as the MERO system and is sold by Unistrut Corporation of Wayne, Mich. That system uses bolts that are slidably mounted within the ends of tubes, the projecting threaded ends of the bolts engaging a correspondingly threaded hole in the joint. Drive collars having a hexagonal-shaped outer surface slide over the projecting ends of the bolts. The drive collars have slots formed in a pair of opposing sides. The protruding ends of a pin that extend through the bolt are received in longitudinal slots that are formed in the drive collars. So configured, the drive collar is capable of rotating the bolt while being axially slidable along it, thereby providing a means for threading the bolt into the hole in the joint. Such a drive collar must be formed by special machining tools and is thus relatively expensive to manufacture.
While known systems have been found satisfactory for conventional structural applications, there is no provision in these systems for preventing rotation of the strut with respect to the bolt once it is connected. In the structural framework employed by applicant, the struts comprise, in part, cylindrical wooden and metal beam members, which are suitable for playground climbing. Hence, it is important that the beam members do not spin about their longitudinal axes while children are climbing upon them.